Showing papers by "Uma Divakaran published in 2020"
TL;DR: In this paper, the authors consider a quantum engine powered by dissipative energizing and relaxing baths and show that the output work is governed by the Kibble-Zurek mechanism, i.e., it exhibits a universal power-law scaling with the driving speed.
Abstract: We demonstrate the existence of universal features in the finite-time thermodynamics of quantum machines by considering a many-body quantum Otto cycle in which the working medium is driven across quantum critical points during the unitary strokes. Specifically, we consider a quantum engine powered by dissipative energizing and relaxing baths. We show that under very generic conditions, the output work is governed by the Kibble-Zurek mechanism, i.e., it exhibits a universal power-law scaling with the driving speed through the critical points. We also optimize the finite-time thermodynamics as a function of the driving speed. The maximum power and the corresponding efficiency take a universal form, and are reached for an optimal speed that is governed by the critical exponents. We exemplify our results by considering a transverse-field Ising spin chain as the working medium. For this model, we also show how the efficiency and power vary as the engine becomes critical.
25 citations
TL;DR: In this paper, the authors study the non-equilibrium dynamics due to slowly taking a quasiperiodic Hamiltonian across its quantum critical point and verify the Kibble Zurek scaling which predicts a power law scaling of the density of defects generated as a function of the rate of variation of the Hamiltonian.
Abstract: We study the non-equilibrium dynamics due to slowly taking a quasiperiodic Hamiltonian across its quantum critical point. The special quasiperiodic Hamiltonian that we study here has two different types of critical lines belonging to two different universality classes, one of them being the well known quantum Ising universality class. In this paper, we verify the Kibble Zurek scaling which predicts a power law scaling of the density of defects generated as a function of the rate of variation of the Hamiltonian. The exponent of this power law is related to the equilibrium critical exponents associated with the critical point crossed. We show that the power-law behavior is indeed obeyed when the two types of critical lines are crossed, with the exponents that are correctly predicted by Kibble Zurek scaling.
14 citations
18 Nov 2020
TL;DR: In this article, it was shown that when the operation of a quantum machine drives the working substance across a phase transition, its finite-time thermodynamics is universal, i.e., it is known to all quantum machines.
Abstract: The authors show that when the operation of a quantum machine drives the working substance across a phase transition, its finite-time thermodynamics is universal.
7 citations